Camphor has been used as an effective repellent and pesticide to stored products for a long history, but Orthaga achatina(Lepidoptera: Pyralidae) has evolved to specifically feed on the camphor tree Cinnamomum camphora. However, the behavioral response of O. achatinato camphor and the molecular basis of camphor perception are totally unknown. Here, we demonstrated that both male and female adults were behaviorally attracted to camphor, suggesting the adaptation of O. achatinato and utilization of camphor as a signal of C. camphora. Second, in 40 O. achatina ORgenes obtained by analyzing antenna transcriptomes, only OachOR16/Orco significantly responded to camphor in the Xenopusoocyte system. Finally, by molecular docking analysis and site-directed mutagenesis, the Ser209 residue is confirmed to be essential for binding of the oachOR16 with camphor. This study not only reveals the camphor-based host plant choice and olfactory mechanisms of O. achatinabut also provides a molecular target for screening more potential insect repellents.